Conveyor for developer apparatus

ABSTRACT

Apparatus for conveying two-component developer material from a developer sump to an elevated location for cascade development in a xerographic reproducing machine. The apparatus includes an endless flexible belt having a series of cavities transverse to the direction of its movement. The belt passes over a drive pulley located in the sump area and a second pulley located at a higher elevation. The belt cavities which normally are in a closed position when in a relaxed state will open as they move around the pulley. As the belt passes the curvature of a lower drive pulley, the cavities will open and then close entrapping the developer material scooped up in the sump area. When the cavities are again forced open to release the entrapped material at the higher elevation onto an input chute for being cascaded across the xerographic surface to be developed.

' United States Patent [1 1 Hewitt June 26, 1973 CONVEYOR FOR DEVELOPER APPARATUS Robert E. Hewitt, Ontario, NY.

[73] Assignee: Xerox Corporation, Stamford, Conn.

[22] Filed: June 28, 1971 [21] App]. No.2 157,249

[75] Inventor:

[52] US. Cl. 198/140, 198/184 [51] Int. Cl. 865g 17/12, 865g 17/.16 [58] Field of Search 198/179, 184, 193, 198/140; 222/371, 415; ll7/17.5; 118/637 [56] References Cited UNITED STATES PATENTS 2,988,199 6/1961 Pinkham 198/179 X 3,342,310 9/1967 Gray 198/179 Primary Examiner-Edward A. Sroka V w A ttorney-James J. Ralabate, Melvin A. Klein et al.

[57] ABSTRACT Apparatus for conveying two-component developer material from a developer sump to an elevated location for cascade development in a xerographic reproducing machine. The apparatus includes an endless flexible belt having a series of cavities transverse to the direction of its movement. The belt passes over a drive pulley located in the sump area and a second pulley located at a higher elevation. The belt cavities which normally are in a closed position when in a relaxed state will open as they move around the pulley. As the beltpasses the curvature of a lower drive pulley, the cavities will open and then close entrapping the developer material scooped up in the sump area. When the cavities are again forced open to release the entrapped material at the higher elevation onto an input chute for being cascaded across the xerographic surface to be developed.

1 Claim, 2 Drawing Figures Pmminmzs I975 3.741.372

m/vavran ROBERT E. HEWITT ATTORNEY CONVEYOR FOR DEVELOPER APPARATUS This invention relates to improved apparatus for loading and unloading developer material into a cascade development zone. More particularly, this invention relates to apparatus suitable for use in transporting two component xerographic developer from a reservoir or sump to an elevated location for being cascaded over the surface of a xerographic member and back to the sump for recirculation for reloading.

In one of the more common forms of developing latent electrostatic images, as described for example in U. S. Pat. No. 3,301,126 issued to R. F. Osborne et al, development occurs by cascading a mixture of carrier granules and toner particles over the surface of the xerographic plate containing the latent electrostatic image. In the two-component developer, the carrier beads or granules and toner particles or powder are mixed together and agitated so that a triboelectric charge is generated therebetween to attract them to each other. The xerographic plate is usually in the form of a cylindrical member such as a drum which is developed by raising the developer material from a sump to an elevated location above the drum so that it may be allowed to pour or cascade over the portion of the surface of the rotating drum to be developed. While in moving contact with the surface of the drum, the developer material selectively deposits toner thereon because the electrostatic charge field in image areas of the plate is greater than the triboelectric charge holding the toner to the carrier beads.

In the past, the developer has been elevated to its raised location for being cascaded over the drum by the use of a bucket conveyor belt system as described for example in the above referred to Osborne patent. The endless belts are used to transport elongated rectangular buckets which carry the developed from a reservoir to unload the contents of each bucket onto an input chute. The developer then, through the force of gravity, cascades down the chute and over the xerographic drum contacting latent images thereon for their development. The developer then gravity flows down a pickoff baffle to the sump portion for being recascaded in a continuing development cycle. Toner may be added to the mixture to replace that lost to the mixture through the normal development of images.

This type of bucket conveyor belt system, although effective, is cumbersome and comprises numerous elements including a multitude of trays or buckets. Since it is necessary to attach buckets to the belt for transporting the developer material, the system is bulky and subject to malfunction. Also space must be provided in the developer housing for clearance of the buckets as they pass the chute and as they move through the sump area. In addition, the bucket conveyor requires numerous assemblying operations and is costly to produce.

The present invention is an improved conveyor to eliminate the use of such space which is at a premium in a continuous and automatic xerographic reproducing machine. This is accomplished, generally speaking, by replacing the buckets with an elastic belt which contains in its own configuration cavities that transport the developer material.

By this arrangement the present invention is an improvement over the bucket conveyor belt system as described above in that it provides a transport which is cheaper, easier to manufacture, more compact,'contains less parts to be moved or fabricated, and is less likely to malfunction or be repaired. Moreover, it has been observed that the life of the developer material is extended.

It is therefore an object of this invention to improve developer transport systems.

It is a further object of the instant invention to facilitate conveying developer material for cascade development systems.

It is yet a further object of this invention to achieve transporting developer material from a sump or reservoir area to an elevated location for being cascaded across the xerographic surface in a manner more simple than theretofore.

It is a further object of the instant invention to enhance moving two component developer material in a continuous cycle of operation with minimal space and machine tolerance requirements.

Further objects of the invention together with additional features and advantages thereof will become apparent from the following description of embodiments of the invention when read in conjunction with the accompanying drawings, wherein:

FIG. 1 is a schematic side view of the improved conveying apparatus arranged in the developer housing of a continuous and automatic xerographic reproducing machine or the like, and

FIG. 2 is an enlarged partial isometric view of the conveying apparatus illustrating certain details in the construction of a developer carrying cavity.

The developer conveyor apparatus of the invention indicated generally as 10 is arranged at the development station of a xerographic copier through which a xerographic drum 11 bearing electrostatic latent images to be developed is advanced as shown by the arrow. The apparatus includes a belt 12 trained around a pair of rollers 14 and 16, one of which 14, is adapted to be driven by any convenient power source such as motor 17 to move in the direction indicated by the arrow. Each of the rollers is mounted for rotation in the frame portion 18 of the developer housing so that the developer material may not leak therefrom.

The lowermost roller 16 is located in the sump or reservoir portion 20 of the developer housing. The sump is adapted to be provided with a mass of developer 22 to substantially submerge the lowermost reaches of the belt therein. The front and back walls 24 and 26 of the developer housing taper toward each other so that developer material falling from the drum and directed by pickoff baffle 28 may flow into the toner loading area of sump 20 for the conveyor.

The upper roller 14 is positioned above the lowermost roller 16 in an area above the cascade develop ment zone. It is preferably mounted slightly offset from the lowermost roller tilting toward the development zone to facilitate the removal of developer therefrom as will be later described. A developer input chute 26 is provided to receive developer from the belt at an intermediate portion thereof for guiding the developer toward the development zone. The belt 12 is constructed of an elastomeric material that has cavities 30 formed within the front portion 32 of the belt body which are adapted to carry developer material. The backside'34 of the belt body is adapted to engage a drive system including rollers 14 and 16. A belt of this type could be extruded from an elastic material or molded in two pieces. The belt may comprise one or more layers of elastomeric material. Desirably the top layer is inert with respect to developer so that it will not interact with the materials of developer to cause a deterioration in the properties of the toner or carrier. Any suitable elastomeric material may be used for this purpose. Preferably a rubber material under the trade name Hypolon, commercially available from the Du- Pont Corporation, a Corporation of Delaware, has been found to work well.

When motor 17 is actuated during the running of the xerographic copier, belt 12 is moved in the direction indicated by the arrow. As the individual cavities 30 of the belt move around the lower roller 16, the roller causes the cavities to open. As the belt moves, the cavities will leave the curvature of roller 16 and will subsequently close. A mass of developer is provided to sub-' merge the lowermost reaches of the belt so that the cavities only close while in the developer mass. This action will encompass and entrap the developer in the hollow cavities 30. The developer is therefore transported within cavities 30 until the individual cavities reach the upper roller 14 at an elevated location. When the cavities move around the curvature of roller 14, the cavities are forced to expand and open. This action allows the developer entrapped in the belt cavities to be released. The developer will then flow down chute 26 so as to be cascaded across the xerographic surface in the development zone. The cascaded developer will then be dropped from the development zone and recollected in sump 20 for recycling through the conveyor system and xerographic development zone.

In the disclosed embodiment, the quantity of developer conveyed thereby is easily varied by the size of the belt and its cavities and by the speed of the belt. It is preferred also that the rollers be constructed of a material to give good frictional contact between the belt and the surface of the roller to prevent slipping therebetween. This frictional material could alternatively or additionally be on the backside 34 of the belt.

It should be understood that the back portion of the belt could also be reinforced to yield extra strength and could be constructed with indented portions which mate with teeth in the rollers.

The belt construction of FIG. 2 illustrated in more detail the shape of cavities 30. The cavities are sufficiently deep to transport large amounts of developer to the elevated location. At the elevated location dumping is effected due to expansion of a slit 36 formed in the belt in communication with each of the cavities 30 as the cavities are urged open by the curvature of roller 14. In similar fashion loading developer into the cavities is achieved in the vicinity of roller 16.

By the above invention a xerographic developer system is described which is compact, easy to manufacture and is unlikely to have malfunction problems. Also due to the simple manner in which developer material is handled, the life of developer material is greatly extended providing economic advantages to the machine user.

While the instant invention as to its object and advantages has been described as being carried in a specific embodiment hereof it is not intended to be limited thereby but it is intended to be covered broadly within the scope of the appended claims.

What is claimed is:

1. In a xerographic copying machine in which a xerographic drum is rotated past processing stations including a development station in which developer material is cascaded over the drum surface, the improvement comprising conveying apparatus to transport developer material at a developer sump from a first location to a second location at the beginning or a cascade development zone comprising a first roller positioned at the first location, a second roller positioned at the second location, an endless elastomeric belt member having a width coextensive with the development zone an internal face portion and an external face portion, said belt member being arranged over said rollers with said internal face engaging said rollers drive means coupled to one of said rollers to move said belt member along a predetermined path,

said external face portion being formed with elongated spaced cavities having a tapered portion defining a leading edge and arranged with a longitudinal dimension perpendicular to the direction of travel of the belt member and each presenting a slit transverse to the direction of movement which slit is in a closed position when said belt member is relaxed along its path, the slit being urged open as the belt member passes around said rollers at the first and second locations to effect loading by scooping developer material with the tapered portion into the cavity and then sealing the cavity to prevent spillage and then unloading developer material in the aforementioned development zone, respectively. 

1. In a xerographic copying machine in which a xerographic drum is rotated past processing stations including a development station in which developer material is cascaded over the drum surface, the improvement comprising conveying apparatus to transport developer material at a developer sump from a first location to a second location at the beginning or a cascade development zone comprising a first roller positioned at the first location, a second roller positioned at the second location, an endless elastomeriC belt member having a width coextensive with the development zone an internal face portion and an external face portion, said belt member being arranged over said rollers with said internal face engaging said rollers drive means coupled to one of said rollers to move said belt member along a predetermined path, said external face portion being formed with elongated spaced cavities having a tapered portion defining a leading edge and arranged with a longitudinal dimension perpendicular to the direction of travel of the belt member and each presenting a slit transverse to the direction of movement which slit is in a closed position when said belt member is relaxed along its path, the slit being urged open as the belt member passes around said rollers at the first and second locations to effect loading by scooping developer material with the tapered portion into the cavity and then sealing the cavity to prevent spillage and then unloading developer material in the aforementioned development zone, respectively. 